Nutating engines are well known in the patent literature, and are well described in the following patents:
U.S. Pat. No. 3,492,974 to Kreineyer
U.S. Pat. No. 4,877,379 to Okabe.
As used herein the word engine is used in its broadest sense to define a mechanism which may be used as a pump for pumping fluids including compressible and noncompressible fluids and as an internal or external combustion engine, for example.
Although nutating engines have excited considerable interest, this has been largely confined to paper proposals, in part due to difficulties in machining the relatively complex surfaces, and also in part due to wear problems, sealing problems and gearing problems. The first two problems are somewhat interrelated. In the engines of the prior art, the nutating action of the rotor arises from the face to face contact of confronting, relatively rotating surfaces, which define between them the variable volume pockets of the engine within which, for example, a gas may be compressed or expanded. Difficulty is often experienced in lubricating these confronting surfaces, and wear may be relatively high on the rubbing portions of the surfaces, leading to rapid wear and a loss of seal between adjacent pockets.
Typically in a nutating engine one of the relatively rotating surfaces has three cavities alternating with three sharply defined cusps, and the other surface has two rounded, diametrically opposed cusps alternating with two shallow cavities. In such engine, when the parts are relatively rotated so that the rotor defining one of the pockets is in a position which, in an equivalent piston engine would be referred to as bottom dead centre, the rotor will at the same time define an adjacent pocket which would be equivalent to that where a piston would be at top dead centre in a piston engine. In this relative position of the rotory engine, the pressure in the one pocket is at a minimum while the pressure is an adjacent pocket is at a maximum. The seal between these two pockets comprises a sharply defined cusp which contacts a shallow cavity adjacent to its maximum radius of curvature, whereby the area of contact and interfering proximity between the adjacent confronting surfaces is at a minimum.